The present invention is directed to a communications interface apparatus adaptable for use in effecting communications between an analog device and a digital device. Specifically, in its preferred embodiment, the present invention effects communications between a voice-band device, such as a telephone, and a data processing device.
The present invention receives analog signals from a voice-band device, decimates those analog voice-band signals to produce decimated incoming digital signals representative of the received analog voice band signals. The decimated incoming digital signals are recognizable by the data processing device.
The present invention also receives outgoing digital signals from the data processing device, interpolates those outgoing digital signals to produce an interpolated digital signal which is converted to an outgoing analog signal representative of the outgoing digital signal. The outgoing analog signal is recognizable by the analog device.
In the manufacturing of interface devices such as the present invention, it is common that separate duplicate components be utilized for the analog-to-digital conversion circuitry and the digital-to-analog conversion circuitry. It is also common that separate components are used for the decimation of incoming audio signals and for the interpolation of outgoing digital signals. Often there is duplication of components between the decimation circuitry and the interpolation circuitry.
Such use of duplicate components results in several disadvantages. For example, in integrated circuit embodiments, the cost increase occasioned by such component duplication is not significant. However, such duplicate components require additional trimming during manufacture in order that gains, accuracy, and offsets and biases are balanced within the analog-to-digital functional path and within the digital-to-analog functional path.
Another disadvantage is that the use of duplicate components necessarily requires that a greater chip area be occupied. Thus, the smallness of a chip implementation of such a device is inherently limited by the necessity to duplicate components to effect the two functions required.
The present invention is designed to overcome some of the shortcomings of duplicate-component interface apparata for use in effecting communications between analog and digital devices.